1. Field of the Invention
The present invention relates to a liquid crystal display device and a manufacturing method thereof. Particularly, the present invention relates to a liquid crystal display device using a sealing member containing a photo curing material, and a manufacturing method thereof.
2. Description of the Related Art
Conventionally, liquid crystal display devices have been widely used as substitution for CRTs. The liquid crystal display devices are thinner than the CRTs and can be downsized, so that the liquid crystal display devices are used for mobile terminals such as laptop PCs and mobile phones.
An active matrix type liquid crystal display device of these liquid crystal display devices has been mainly used in recent years. The active matrix type liquid crystal display device is arranged such that an array substrate on which thin film transistors (TFT) are formed in a matrix manner and a CF substrate on which a color filter (CF) and so on are formed are disposed face to face and are bonded together by a thermal curing sealing member provided on the respective circumferential end portions of the substrates. Between the substrates, a liquid crystal having an electro-optic property is provided.
Such a liquid crystal display device is manufactured by bonding the substrates together via the sealing member, injecting the liquid crystal from an opening section provided in a sealing pattern of the sealing member, and sealing the opening section of the sealing pattern thereafter.
However, it takes a long time to inject the liquid crystal upon manufacturing the liquid crystal display device in the manner described above. In view of this, a liquid crystal dropping adhesion method is employed. The liquid crystal dropping adhesion method is a method of injecting a liquid crystal in vacuum by applying a sealing member to the array substrate in the form of a frame along the circumferential ends of the array substrate, dropping the liquid crystal onto the portion surrounded by the sealing member thus applied, and bonding the array substrate and the CF substrate together.
However, in the above method, when the liquid crystal and the sealing member uncured meet, an ingredient of the sealing member is melt into the liquid crystal. This results in occurrence of spots. Further, heat application required in curing the sealing member causes thermal expansion of the array substrate and the CF substrate used herein, with the result that the substrates are displaced from each other. Required accordingly are: (i) fast curing for prevention of the spots, and (ii) a sealing member that is cured without heat application and therefore allows prevention of the displacement. It has been proposed to use a photo curing sealing member instead of the thermal curing sealing member.
FIG. 8 is a plan view illustrating a panel section of a liquid crystal display device using such a photo curing sealing member. FIG. 9 is a cross sectional view schematically illustrating the structure of the liquid crystal display device shown in FIG. 8 and taken along line B-B. The following explains the conventional sealing member used in the liquid crystal display device, with reference to FIG. 8 and FIG. 9.
The panel section of the liquid crystal display device includes a CF substrate 101 and an array substrate 102, between which a liquid crystal 106 is interposed. The CF substrate 101 and the array substrate 102 are bonded together via a photo curing sealing member 103. The CF substrate 101 has a surface which meets the sealing member 103 and on which a light blocking black matrix (hereinafter, referred to as “BM”; light blocking film) 105 is formed. The array substrate 102 has a surface which meets the sealing member 103 and on a part of which metal wires 104 (see FIG. 9) are formed so as to supply a signal to a display area 109. The metal wires 104 are connected to terminal sections 111. The sealing member 103 is provided in a frame region 110 surrounding the display area 109.
When light is irradiated via the array substrate 102 in a manufacturing process of the liquid crystal display device so as to cure the sealing material 103, each of the metal wires 104 shades a portion 103a (see FIG. 9) of the sealing member 103, with the result that the light is unlikely to irradiated onto the portion 103. Accordingly, the sealing member 103 is likely to stay uncured. The light may travel around due to a diffraction effect; however, in this case, the light needs to be irradiated for a long time.
A conceivable way to overcome this shortcoming is to provide an opening section (light transmission section) in the BM 105 (light blocking film) making contact with the photo curing sealing member 103 interposed between the two substrates and to irradiate light via the opening section. Normally, such an opening section can be formed in a part of the BM 105 (light blocking film) as long as the formation of the opening section has no adverse effect on input/output signals of the frame region 110.
For example, Patent Document 1 (Japanese Unexamined Patent Publication Tokukai 2000-89235 (published on Mar. 31, 2000) corresponding to U.S. Pat. No. 6,424,394 (registered on Jul. 23, 2002)) proposes that the shape of the light blocking film provided just above or just below the photo curing sealing member, the width thereof, and the size of the opening section provided in the light blocking film are defined such that the photo curing sealing member is irradiated with light necessary for curing the photo curing sealing member.
Another conceivable way to overcome the aforesaid shortcoming is to use a light blocking layer in which a blue-colored layer, a red-colored layer, and a green-colored layer are provided on top of one another, instead of using the BM 105 provided on the CF substrate 101.
For example, Patent Document 2 proposes to use the light blocking layer such that the blue-colored layer is in contact with the sealing member and to use as the sealing member a resin material reactive to light having a wavelength falling within the blue band. Specifically, Patent Document 2 (Japanese Unexamined Patent Publication Tokukai 2001-222017 (Published on Aug. 17, 2001) corresponding to US Unexamined Patent Publication 2002/0196393 (published on Dec. 26, 2002)) proposes to cure the sealing member by light irradiated via the CF substrate so as to pass through the blue-colored layer and therefore having a wavelength falling within the blue band.
Meanwhile, Patent Document 3 (Japanese Unexamined Patent Publication Tokukai 2004-4563 (published on Jan. 8, 2004) corresponding to US Unexamined Patent Publication 2003/0218713 (published on Nov. 27, 2003)) proposes to cure the sealing member by irradiating light obliquely with respect to the substrate surface of the CF substrate such that the light having passed through the CF substrate is reflected by the array substrate, the BM, and the metal wires and therefore reaches the overlapping region of the sealing member with each of the metal wires.
However, even when the method described in Patent Document 1 is used, it is still difficult to cure the portion 103a (see FIG. 9) shaded by each of the metal wires 104 as compared with portions other than the portion 103a, as long as the light is irradiated from the metal wire 104 side so as to cure the sealing member 103. On the other hand, in the methods described in Patent Documents 2 and 3, designing of the liquid crystal panel and the way of irradiating the light are complicated and light utilization efficiency is not good.
Accordingly, demands arise in (i) a liquid crystal display device manufacturing method which prevents spots from appearing due to poor curing of a sealing member, and (ii) the liquid crystal display device in which the problem of the spots appearing due to the poor curing of the sealing member is solved.